The present invention relates to controllers for opening and closing a fluid channel.
Controllers are already known which include those adapted to close a fluid channel by a valve stem biased downward by a spring and to open the fluid channel by driving the valve stem upward with a force of pneumatic pressure, solenoid, or the like, which is greater than the force of the spring, and those adapted to open a fluid channel by a valve stem biased upward with a spring and to close the fluid channel by urging the valve stem downward with a force of pneumatic pressure, solenoid, or the like, which is greater than the force of the spring.
In the case where such conventional controllers are used for high-pressure fluids, there arises a need to use an increased force for closing the fluid channel to prevent leakage of the fluid. However, the controller wherein the valve stem is biased downward by a spring to close the fluid channel and driven upward by pneumatic pressure, solenoid, or the like, to open the fluid channel has the problem that the channel closing force cannot be increased as required, because an increase in the force of the spring necessitates an increase in the pneumatic, or like, force for driving the valve stem but the increase in the driving force is limited. The controller wherein the valve stem is biased upward by a spring to open the fluid channel and urged downward with a force of pneumatic pressure, solenoid, or the like, which is greater than the spring force to close the fluid channel has a similar problem since an increase in the channel closing force requires an increase in the pneumatic, or the like downward urging force.